While I have never encountered any special sort of "break in" oil for filling the crankcase the first time please be aware that many/most engine manufacturers use a ZDP rich assembly lube on critical components (bearings, bearing journals, cam lobes, etc....). This additional assembly lube "pollutes" the factory fill of engine oil (which in all likelyhood is plain engine oil) adding a significant amount of the anti-wear ZDP compound to that first crankcase full of oil. So...while the oil installed by the OEM wasn't special by itself the addition of the assembly lube DOES create a sort of breakin oil mixture that provides extra anti-wear protection when the engine is green. The extra dose of ZDP will also keep the concentration of ZDP at a sufficient level for wear protection during the first oil change interval as the green engine will be depleting the ZDP more rapidly during breakin when parts are burnishing and mating at critical surfaces. That is one reason that the first oil change interval can go the full distance even though the engine is breaking in and taking more out of the oil during the first fill.